Cell service shows disconnected in diagnostics

I have had the original Simplisafe for years and never had a issue. Over the new Year I upgraded to the current one and from day one when I go to the system diagnostics screen it shows the cell service is disconnected. I have called tech support and they walked me through a few things. Finally they said they will send me a new base station with a T Mobile sim instead of Verizon. I received the ne base station last week hooked it up and still the same issue. They sent another Verizon base station. The second tech told me that do not use T Moblie anymore. So I spent the better part of the day on the phone with a few different techs and still no luck, we reset the base station the keypad they set updates nothing worked. They did say they are getting a single at their end. Finally the last person I spoke with said oh that normal if your are also connected to WIFI. To be honest I don't live him because why would everyone else be trying to fix this problem. So now I wonder what I should do. They system seen to work fine but am I just relying on my wifi single? Does anyone out there have their system on WIFI and their diagnostics screen show cell disconnected?
Thanks